Sodium channel alpha subunits

ABSTRACT

The present invention discloses the cDNA sequence and the expressed amino acid sequence of a sodium channel α subunit, termed hH1b. A specific mutation in hH1b has been shown to display a different phenotype in relation to a human heart disease than other known human sodium channel α subunits with corresponding mutations. The present inventions provides new tools to design or identify new diagnostic and treatment strategies or agents for sodium channel related diseases or conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] This invention was made with United States government support awarded by the following agency: NIH, Grant No. HL-56441. The United States has certain rights in this invention.

BACKGROUND OF THE INVENTION

[0003] Sodium channel proteins embedded in cellular membranes of muscle cells, neurons and other excitable cells help produce and propagate electrical impulses and are implicated in many human diseases and conditions. Sodium channels are often composed of a pore-forming α subunit, having four homologous domains DI-DIV and six transmembrane regions S1-S6 per domain, and two auxiliary subunits β1 and β2. The α subunit is sufficient to form a functional channel for generating sodium current flow across cellular membranes.

[0004] Human cardiac sodium channels play a critical role in cardiac excitation. hNa_(v)1.5, a human cardiac sodium channel α subunit encoded by the SCN5A gene forms a functioning monomeric sodium channel that carries the inward Na current (I_(Na)) in the heart. The I_(Na) current is vital for excitation and conduction in working myocardium and in specialized conduction tissue such as Purkinje fibers.

[0005] Two distinct full-length polymorphic SCN5A clones (designated SCN5A hH1 and SCN5A hH1a, or simply hH1 and hH1a, respectively) that encode the hNaV1.5 human cardiac sodium channel have been isolated from human cardiac cDNA libraries (Gellens, M. E. et al., “Primary structure and functional expression of the human cardiac tetrodotoxin-insensitive voltage-dependent sodium channel,” Proc.Natl.Acad.Sci. U.S.A. 89, 554-558 (1992); Hartmann, H. A. et al., Effects of III-IV linker mutations on human heart Na⁺ channel inactivation gating. Circ.Res. 75, 114-122 (1994)). The significance of polymorphisms in the sodium channel is still unknown. For example, it is not known how such polymorphisms affect the mutation phenotype of SCN5A. Nonetheless, identified polymorphisms can help identify disease-associated mutations in SCN5A. For example, various SCN5A mutations are associated with congenital Long QT syndrome, idiopathic ventricular fibrillation and the Brugada syndrome (Keating and Sanguinetti 2001).

[0006] The reported sequences for hH1 and hH1a differ by nine amino acids with hH1 containing one additional amino acid (Q1077). However, the applicants independently sequenced both SCN5A forms again, thereby confirming the sequence of hH1a, while noting that the re-sequenced hH1 differed from the published hH1 sequence at seven amino acid positions, where each difference is, in fact, identical to the hH1a sequence. This change in the published sequence reduces the difference between hH1 and hH1a to just 3 amino acids (T559 vs. A559, Q1027 vs. R1027, and Q1077 vs. Q1077del (hH1 vs. hH1a, respectively) over a total length of 2016/2015 amino acids, respectively. All of the differences are confined to the cytoplasmic linkers between DI-II and between DII-III. Both hH1 and hH1a contain a histidine residue at amino acid 558 (H558), the site of a histidine-to-arginine polymorphism (H558R) (Iwasa, et al., “Twenty single nucleotide polymorphisms (SNPs) and their allelic frequencies in four genes that are responsible for familial long QT syndrome in the Japanese population,” J.Hum.Genet. 45, 182-183). The amino acid numbering follows that of the original hH1 clone which contains 2016 amino acids. In separate studies, the two known polymorphic forms showed only minor kinetic differences that can be attributed to different expression systems and study techniques including solutions, temperature, and protocols. (Gellens, M. E. et al., supra; Hartmann et. al., supra; and Wattanasirichaigoon et. al. 1999). Subtle differences in kinetics such as decay rates, inactivation midpoints, and late I_(Na), however, may be important in controlling repolarization.

[0007] Sodium channel α subunits encoded by an SCN5A hH1a clone carrying an arrhythmogenic missense methionine-to-leucine mutation at amino acid 1766 (M1766L) further exhibit a significant inward sodium current level drop, relative to the current level in channels encoded by a wild type hH1a clone. Recently, M1766L in the hH1a background was shown to have a trafficking defect and to cause QT prolongation and ventricular arrhythmia (Valdivia et. al. 2001). These conditions can be rescued by low temperature, antiarrhythmic drug and β1 subunit (Valdivia et. al. 2001).

[0008] In another aspect, drugs that can alter sodium channel activities can relieve or prevent symptoms of certain conditions such as cardiac arrhythmias. Cardiac arrhythmias are abnormalities in the rate, regularity, or site of origin of the cardiac impulse, or a disturbance in conduction of the impulse that alters the normal sequence of atrial or ventricular activation. One known way to treat cardiac arrhythmias is to block the activity of a cardiac sodium channel. Sodium channel blockers used to treat cardiac arrhythmias include: Quinidine, Lidocaine, Procainamide, Mexiletine, Flecainide, Moricizine, and Disopyramide. Identifying other polymorphic forms of human cardiac sodium channel will advance our understanding of sodium channel-related heart problems and provide new tools for developing diagnostic, prophylactic and therapeutic strategies.

BRIEF SUMMARY OF THE INVENTION

[0009] The present invention discloses a novel polymorphism in the hNaV1.5 sodium channel α subunit polypeptide, designated SCN5A hH1b or simply hH1b, as well as a nucleic acid molecule encoding same. A specific mutation in hH1b displays a different phenotype in relation to a human heart disease than other known human sodium channel α subunits carrying a corresponding mutation.

[0010] The present invention also includes various related nucleic acid molecules and polypeptides that are useful in various applications such as detecting the subunit and generating antibodies to the subunit. The present invention also relates to cloning and expression vectors and host cells containing same. In addition, the present invention includes methods for screening for an agent for altering (increasing or reducing) sodium channel activities. Furthermore, methods of using the nucleic acids and polypeptides to detect hH1b and generate antibodies to detect and purify hH1b are also included in the present invention. New diagnostic and treatment strategies for various sodium channel-related diseases and conditions are also enabled by the present invention.

[0011] It is an object of the present invention to identify a new polymorphic form of a human cardiac sodium channel.

[0012] It is another object of the present invention to provide new tools for designing diagnostic and treatment strategies for sodium channel related diseases and conditions.

[0013] Other objects, advantages and features of the present invention will become apparent from the following specifications and claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0014]FIG. 1 depicts the structure of the hNaV1.5 sodium channel α subunit polypeptide including amino acid variations among hH1, hH1a, and hH1b.

[0015]FIG. 2 shows whole cell I_(Na) for hH1, hH1a, and hH1b.

[0016]FIG. 3 shows current magnitude for wild type and hH1, hH1a, and hH1b clones and for each clone containing the M1766L arrhythmia mutation.

[0017]FIG. 4 summarizes the data of FIG. 3 as relative I_(Na) density.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates to a new variant form of the hNa_(v)1.5 sodium channel α subunit, designated SCN5A hH1b. A polynucleotide sequence that encodes SCN5A hH1b is attached as SEQ ID NO: 1. The amino acid sequence of the polypeptide encoded by SCN5A hH1b is attached as SEQ ID NO:2. The new clone differs from SCN5A hH1 by just four amino acids in the cytoplasmic linkers between DI-DII and DII-DIII (R558 vs. H558, 1618 vs. L618, R1027 vs. Q1027, and Q1077del vs. Q1077 (hH1b vs. hH1, respectively)). SCN5A hH1b differs from SCN5A hH1a by just three amino acids in the cytoplasmic linker between DI-DII (R558 vs. H558, T559 vs. A559, and I618 vs. L618 (hH1b vs. hH1a respectively). The only two amino acid positions at which hH1b differs from both hH1 and hH1a are amino acids 558 and 618. Table 1 summarizes the differences among the three hNa_(v)1.5 clones and from a sequence found in the Celera® human genome database. BLAST searching of the Celera human genome sequence showed only 2 differences between hH1b and the Celera sequence (R558 vs. H558 and I618 vs. L618), both of which are in the cyotplasmic linker between DI-DII. FIG. 1 also depicts the set of relevant mutations in the various clones, as well as the M1766L mutation. TABLE 1 Deduced amino acid sequence comparisons for SCN5A clones. AA# hH1 HH1a hH1b ® Celera 558 H H R H 559 T A T T 618 L L I L 1027 Q R R R 1077 Q . . .

[0019] The hH1, hH1a, and hH1b sodium channel α subunits exhibits similar activation, inactivation and recovery kinetics when expressed in a cell line and, accordingly, hH1b provides an additional target for diagnosing and treating sodium channel-related diseases or conditions or for determining an agent's effects on sodium ion channels. More interestingly, hH1b differs from hH1 and hH1a in that the sodium channel current of the hH1b form is not lost in the presence of the M1766L mutation, as it is in the case of the hH1 and hH1a forms of the SCN5A gene. Because M1766L is associated with long QT syndrome in subjects that carry the hH1a form, the present invention further enables a test for determining the form of SCN5A carried by a subject, thereby facilitating assessment of the subject's risk for developing long QT syndrome or other condition.

[0020] The nucleic acid and amino acid sequences of hH1b disclosed herein enable the skilled artisan to produce diagnostic, prevention and treatment tools for sodium channel-related diseases including probes or hH1b specific antibodies for detecting hH1b expression in a biological sample.

[0021] In one aspect, the present invention relates to an isolated polypeptide comprising the amino acid sequence of SEQ ID NO: 2. An isolated polypeptide, as used herein, is one either synthetically derived or removed from its natural environment. An isolated polypeptide identical to SEQ ID NO: 2 carrying a substitution at one or more non-critical amino acid positions, where the substitution does not materially affect the function of the polypeptide. A non-critical amino acid position is an amino acid at a position other than those disclosed for hH1b in Table 1. Furthermore, an isolated polypeptide of the invention can also include any of the foregoing polypeptides having one or more amino acids at either or both of the N-terminus and C-terminus, where the additional amino acid(s) do not materially affect the function of the polypeptide. A change does not materially affect the function if the protein retains kinetic parameters within the ranges of those disclosed for hH1b in Table 2 and if the protein retains the ability to rescue the M1766L mutation, as described above. Any additional amino acids can, but need not, have advantageous use in purifying, detecting, or stabilizing the polypeptide. Likewise, small deletions or other rearrangements in the polypeptide that do not affect the function of the polypeptide are also within the scope of the invention. Such deletions are preferably deletions of fewer than 100 amino acids, more preferably of fewer than 50 amino acids, still more preferably of fewer than 10 amino acids. TABLE 2 Kinetic parameters for 3 SCN5A clones. hH1 hH1a hH1b Activation V_(1/2) (mV) −44 ± 5  −40 ± 7  −43 ± 6  Slope factor 5 ± 1 5.5 ± 0.6 5.5 ± 0.7 N 10 7  9 Inactivation V_(1/2) (mV)  −95 ± 4.8*  −86 ± 5.8* −90 ± 8.8  N  9 7 10 Recovery τ_(f) (ms) 8 ± 5 5 ± 3 5 ± 2 τ_(s) (ms) 215 ± 101 279 ± 312 111 ± 52  As 0.31 ± 0.1  0.25 ± 0.1  0.24 ± 0.1  N  8 6  9 Decay (−30 mV) τ_(f) (ms) 1.2 ± 0.4 1.5 ± 0.5 1.3 ± 0.5 τ_(s) (ms) 6.4 ± 5   6.0 ± 3   4.0 ± 1   A_(f) 0.71 ± 0.1  0.65 ± 0.1  0.56 ± 0.2  N  9 6  9

[0022] In a related aspect, the present invention also includes an immunogenic fragment of SEQ ID NO: 2 that contains at least one of amino acid 558 and amino acid 618 of SEQ ID NO: 2 and an antibody that binds specifically to such an immunogenic fragment. Such immunogenic fragments are used to generate an hH1b-specific antibody that can be used to detect or to isolate hH1b protein, or both. An hH1b-specific antibody has a higher affinity for hH1b protein than for either hH1- or hH1a protein. It is well within the ability of an artisan having ordinary skill in possession of the disclosed SEQ ID NO: 2 to make monoclonal or polyclonal antibodies against some or all of the polypeptide and to assess the specificity of the antibodies.

[0023] In another aspect, the present invention relates to an isolated nucleic acid containing a polynucleotide having an uninterrupted sequence that encodes a polypeptide of the invention as set forth above. An “isolated nucleic acid” has structure not identical to that of any naturally occurring nucleic acid or to that of any fragment of a naturally occurring genomic nucleic acid spanning more than three separate genes. The term therefore covers, for example, (a) a DNA that has the sequence of part of a naturally occurring genomic DNA molecule but which is not flanked by both of the coding sequences that flank that part of the molecule in the genome of the organism in which it naturally occurs; (b) a nucleic acid incorporated into a vector or into the genomic DNA of a prokaryote or eukaryote in a manner such that the resulting molecule is not identical to any naturally occurring vector or genomic DNA; (c) a separate molecule such as a cDNA, a genomic fragment, a fragment produced by polymerase chain reaction (PCR), or a restriction fragment; and (d) a recombinant nucleotide sequence that is part of a hybrid gene, i.e., a gene encoding a fusion protein. Specifically excluded from this definition are nucleic acids present in mixtures of (i) DNA molecules, (ii) transfected cells, and (iii) cell clones, e.g., as these occur in a DNA library such as a cDNA or genomic DNA library. An isolated nucleic acid molecule can be modified or unmodified DNA or RNA, whether fully or partially single-stranded or double-stranded or even triple-stranded. A modified nucleic acid molecule can be chemically or enzymatically induced and can include so-called non-standard bases such as inosine.

[0024] In a related aspect, any nucleic acid of the present invention described above can be provided in a vector in a manner known to those skilled in the art. The vector can be a cloning vector or an expression vector. In an expression vector, the polypeptide-encoding polynucleotide is under the transcriptional control of one or more non-native expression control sequences which can include a promoter not natively found adjacent to the polynucleotide such that the encoded polypeptide can be produced when the vector is provided in a compatible host cell or in a cell-free transcription and translation system. Such cell-based and cell-free systems are well known to the skilled artisan. Cells comprising a vector containing a nucleic acid of the invention are themselves within the scope of the present invention. Also within the scope of the present invention is a host cell having the nucleic acid of the present invention integrated into its genome at a non-native site.

[0025] The present invention also includes an isolated nucleic acid molecule that contains a fragment of at least 20 contiguous nucleotides of SEQ ID NO: 1 or its complement wherein the fragment includes codon(s) encoding at least one of amino acids 558 and 618 and wherein the fragment hybridizes under stringent hybridization conditions to SEQ ID NO: 1 or its complement. Such a nucleic acid molecule can be used to detect the expression of hH1b in a cell. A stringent hybridization is, for example, hybridizing at 68° C. in 5×SSC/5×Denhardt's solution/1.0% SDS, and washing in 0.2×SSC/0.1% SDS at room temperature. Moderately stringent conditions include washing in 3×SSC at 42° C.

[0026] The present invention also enables a screening method for agents that can either inhibit or enhance sodium channel activities. In such a method, an agent is exposed to a cell line that expresses a functional hH1b and the agent's effect on hH1b activity is determined. hH1b activity can be measured in many ways, including but not limited to measuring a sodium current across the cell membrane, a sodium current kinetic activity, a membrane potential, or an intracellular sodium level. Also, a phenotype associated with over-expression of a sodium channel or absence of expression (e.g., in a transgenic knockout animal) can be monitored. In vitro, an effect on action potential can be measured after a channel of interest is transfected into suitable cells, such as cardiac cells. An arsenal of agents affecting the sodium channel activity are desired because many diseases and conditions, such as arrhythmias and Brugada syndrome, result from elevated or reduced sodium channel activity. Particularly in view of the understanding that various forms of the sodium channel α subunit differ functionally, it is important to evaluate the effects of every form that may be present in an individual. Indeed, one can tailor a suitable treatment to an individual after evaluating the form of α subunit present in that individual. Sodium channel activity means the open channel activity leading to a peak sodium current. Sodium channel activity is enhanced or inhibited when the open state probability is greater or less, and the peak current is higher or lower, respectively, than in the absence of a modulating agent.

[0027] Batteries of agents for screening are commercially available in the form of various chemical libraries including peptide libraries. Examples of such libraries include those from ASINEX (e.g., the Combined Wisdom Library of 24,000 manually synthesized organic molecules) and from CHEMBRIDGE CORPORATION (e.g., the DIVERSet™ library of 50,000 manually synthesized chemical compounds; the SCREEN-Set™ library of 24,000 manually synthesized chemical compounds; the CNS-Set™ library of 11,000 compounds; the Cherry-Pick™ library of up to 300,000 compounds). Once an agent having desired ability to increase or decrease activity of the sodium channel protein is identified, further iterations of the screen using one or more libraries of derivatives of that agent can be screened to identify agents having superior effects.

[0028] The above screening methods also enable one to determine the likelihood that an agent intended to be administered to a human or non-human subject will induce an undesired and unintended side effect, namely by altering the activity of cellular hH1b in a subject in which such alteration is not indicated. Any product of the invention described herein can be combined with one or more other reagent, buffer or the like in the form of a kit useful, e.g., for diagnostic or therapeutic purposes, in accord with the understanding of a skilled artisan.

[0029] The present invention is not intended to be limited to the foregoing, but rather to encompass all such variations and modifications as come within the scope of the appended claims. The invention will be more fully understood upon consideration of the following Examples which are, likewise, not intended to limit the scope of the invention.

EXAMPLES Structural Differences Among Three Complete hNa_(v)1.5 Clones

[0030] We generated a novel, complete hNa_(v)1.5-encoding clone (SCN5A form hH1b) from human cardiac mRNA (Clontech®, Palo Alto, Calif.) using RT-PCR. About 3 kb of 5′ Na_(v)1.5 gene was cloned using 5′-GATGAGAAGATGGCAAACTTC C-3′ (SEQ ID NO: 3) and 5′-GCTCTGGATCCCCGGGGGTGCC-3′(SEQ ID NO: 4) primers. The 3 kb of 3′ Na_(v)1.5 gene was cloned with 5′-CACCCCCGGGGATCCAGAGC-3′ (SEQ ID NO: 5) and 5′-TTCAGTGTGTCCTGGCCAG-3′ (SEQ ID NO: 6) primers. RETRscript (Ambion®, Austin, Tex.) and pfu DNA polymerase were used to perform RT-PCR according to the protocol recommended by the manufacturer. PCR thermocycling involved one denaturation cycle at 94° C. for 1 min, 35 amplification cycles at 94° C. for 1 min, 50° C. for 1 min and 72° C. for 8 min, and one extension cycle at 72° C. for 20 min. The PCR products were cloned into pCR-BluntII-TOPO vector (Invitrogen®, Carlsbad, Calif.). The sequence of the hH1b gene was determined using thermostable polymerases and fluorescently labeled dideoxy terminators and automated DNA sequence analyzers at the University of Wisconsin Biotechnology Center. The two known hNa_(v)1.5-encoding clones (SCN5A forms hH1 and hH1a) were also re-sequenced completely.

Kinetic Studies of the Three Complete hNa_(v)1.5 Clones

[0031] We measured macroscopic !Na of the three clones concurrently (on the same day) under identical conditions in the same experimental whole cell patch-clamp set-up. All techniques, protocols, and analysis techniques are standard and have been previously published (Nagatomo, et al., “Temperature dependence of early and late currents in human cardiac wild-type and long QT Δ KPQ Na⁺ channels,” Am.J.Physiol. (Heart44) 275, H2016-H2024 (1998), incorporated by reference herein as if set forth in its entirety). The pipette solution contained (in mM) 120 CsF, 15 CsCl, 2 EGTA, 5 HEPES and 5 NaCl (pH7.4 with CsOH). Data were recorded at room temperature. Peak I_(Na) and late I_(Na) were obtained after passive leak subtraction as described previously (Nagatomo, supra). Activation and inactivation data were fitted to a standard Boltzmann equation. Recovery and decay data were fitted to a two-exponential equation. Goodness of fit was determined both visually and by a sum of squares errors. One way ANOVA was performed to determine statistical significance among the three groups of mean data. Statistical significance was determined by a P value <0.05.

[0032] The 3 Na_(v)1.5 clones were introduced by transfection into the HEK293 host cell line (commercially available from ATCC) using Superfect (Qiagen®) according to the protocol recommended by the manufacturer. A Green Fluorescent Protein was co-transfected (at 1:10) as a marker to identify transfected cells. The vectors transfected included SCN5A form hH1 cloned into prcCMV vector (Invitrogen®, Carlsbad, Calif.), and forms hH1a and hH1b separately cloned into pcDNA3 vector (Invitrogen). HEK293 cells were cultured as previously described (Nagatomo et. al. 1998). The HEK 293 host cells were harvested 24 hours later to measure macroscopic I_(Na) current.

[0033] The three clones generally showed similar current time courses (FIG. 2a: representative traces were recorded with test potentials of −120 mV to +60 mV from a holding potential of −120 mV). Summary data for activation, steady-state inactivation, and recovery show minor differences (FIG. 2b Current-voltage relationship (left), “steady state” inactivation relationship (middle) and recovery from inactivation relationship (right) for I_(Na): the y-axis represent normalized current; diagrams depicting the voltage clamp protocols are inset into each plot; peak I_(Na) was measured in response to the last depolarizing step and it was then normalized to the maximal peak I_(Na) found; solid symbols represent the mean data for between 6 to 10 experiments (see Table 2 for exact n numbers) with hH1 (square), hH1a (circle), and hH1b (triangle), and the bars represent SD). Although not identical, the kinetic parameters determined by the fitted lines (Table 2) were only statistically different for the midpoint of inactivation for hH1 (−95 mV) versus hH1a (−86 mV). Late I_(Na) measured at 240 ms after the start of the depolarization was no different among the three clones.

[0034] The three SCN5A clones, hH1, hH1a, and hH1b show minor differences in activation, inactivation, and recovery from inactivation kinetics. These parameters were obtained from fitting the individual experiments as in FIG. 2 to the appropriate model equations (Nagatomo, T. et al. (1998)). The fitted kinetic parameters from n experiments were averaged and are reported ±SD. For the Boltzmann fits (activation and inactivation), the parameters are V_(1/2) midpoint and slope factor. For the exponential fits (recovery and current decay), the parameters are τ_(f)—the fast time constant, τ_(s)—the slow time constant, A_(s)—the fractional amplitude of slow component, and A_(f)—the fractional amplitude of fast component. All parameters were analyzed by one-way ANOVA across the 3 clones, and statistically significant values are marked with an asterisk.

Rescue of Expression for the M1766L Mutant by Using the hH1b Background

[0035] By site-directed mutagenesis, the M1766L arrhythmia mutation was engineered into all three clones, expressed in HEK cells, and studied by voltage clamp. Mutations were generated using the Excite® mutagenesis kit (Stratagene®). The mutagenesis method was based on the protocol recommended by the manufacturer. The M1766L mutation was created with 5′-TTCCTCATCGTGGTTAACCTGTACATTGCCATC-3 ′ (SEQ ID NO: 7) and 5′-GGAGATGATGATGTAGGTGG-3′ (SEQ ID NO: 8) primers. The histamine-to-arginine change at position 558 was generated with 5′-CGAGAGCCACCGCGCATCACTGCTG-3′ (SEQ ID NO: 9) and 5° CTCTCCCCCGCTGTGCTGTTTTC-3′ (SEQ ID NO: 10) primers. DNA was isolated and purified using a Qiagen® (Hilden, Germany) column and protocol.

[0036] Examples Of I_(Na) traces show that the amount of current for the M1766L mutant channel was greatly reduced compared to wild type when expressed in hH1 and hH1a, but the current level was surprisingly large when expressed in hH1b (FIG. 3: Examples of I_(Na) traces (protocol inset) for each construct show that M1766L expressed very poorly in hH1 and hH1a, but expressed normally in hH1b; expression levels for the double mutant H558R/M1766L in hH1a were normal). Summary data of FIG. 4 show that for wild type, hH1b and hH1a clones generally expressed more I_(Na) than the hH1 clone. For wild type, but not mutant channels, the data here represent an underestimate of true current density because larger current densities were discarded to assure better voltage control for kinetic measurement. In general, however, wild type hH1 expressed at lower levels than hH1a and hH1b. Currents for M1766L in hH1b were dramatically greater than those for the mutant in hH1 and hH1a and were not affected by selection. I_(Na) were normalized to cell capacitance and mean values shown as a column with SD bar and the number of experiments indicated next to the bar. Without intending to be limited as to the theory underlying the invention, the applicants speculate that the H558R polymorphism underlies the restoration of expression in sodium channels carrying the M1766L mutation. Again using site-directed mutagenesis, we engineered the double mutation H558R/M1766L in the hH1a clone. Now, rather than the 97% reduction in current expression observed previously for M1766L in hH1a, the H558R/M1766L-hH1a mutant manifested a fully restored I_(Na) density (FIGS. 3 and 4).

1 10 1 6091 DNA Homo sapiens CDS (10)..(6054) 1 gatgagaag atg gca aac ttc cta tta cct cgg ggc acc agc agc ttc cgc 51 Met Ala Asn Phe Leu Leu Pro Arg Gly Thr Ser Ser Phe Arg 1 5 10 agg ttc aca cgg gag tcc ctg gca gcc atc gag aag cgc atg gcg gag 99 Arg Phe Thr Arg Glu Ser Leu Ala Ala Ile Glu Lys Arg Met Ala Glu 15 20 25 30 aag caa gcc cgc ggc tca acc acc ttg cag gag agc cga gag ggg ctg 147 Lys Gln Ala Arg Gly Ser Thr Thr Leu Gln Glu Ser Arg Glu Gly Leu 35 40 45 ccc gag gag gag gct ccc cgg ccc cag ctg gac ctg cag gcc tcc aaa 195 Pro Glu Glu Glu Ala Pro Arg Pro Gln Leu Asp Leu Gln Ala Ser Lys 50 55 60 aag ctg cca gat ctc tat ggc aat cca ccc caa gag ctc atc gga gag 243 Lys Leu Pro Asp Leu Tyr Gly Asn Pro Pro Gln Glu Leu Ile Gly Glu 65 70 75 ccc ctg gag gac ctg gac ccc ttc tat agc acc caa aag act ttc atc 291 Pro Leu Glu Asp Leu Asp Pro Phe Tyr Ser Thr Gln Lys Thr Phe Ile 80 85 90 gta ctg aat aaa ggc aag acc atc ttc cgg ttc agt gcc acc aac gcc 339 Val Leu Asn Lys Gly Lys Thr Ile Phe Arg Phe Ser Ala Thr Asn Ala 95 100 105 110 ttg tat gtc ctc agt ccc ttc cac ccc atc cgg aga gcg gct gtg aag 387 Leu Tyr Val Leu Ser Pro Phe His Pro Ile Arg Arg Ala Ala Val Lys 115 120 125 att ctg gtt cac tcg ctc ttc aac atg ctc atc atg tgc acc atc ctc 435 Ile Leu Val His Ser Leu Phe Asn Met Leu Ile Met Cys Thr Ile Leu 130 135 140 acc aac tgc gtg ttc atg gcc cag cac gac cct cca ccc tgg acc aag 483 Thr Asn Cys Val Phe Met Ala Gln His Asp Pro Pro Pro Trp Thr Lys 145 150 155 tat gtc gag tac acc ttc acc gcc att tac acc ttt gag tct ctg gtc 531 Tyr Val Glu Tyr Thr Phe Thr Ala Ile Tyr Thr Phe Glu Ser Leu Val 160 165 170 aag att ctg gct cga ggc ttc tgc ctg cac gcg ttc act ttc ctt cgg 579 Lys Ile Leu Ala Arg Gly Phe Cys Leu His Ala Phe Thr Phe Leu Arg 175 180 185 190 gac cca tgg aac tgg ctg gac ttt agt gtg att atc atg gca tac aca 627 Asp Pro Trp Asn Trp Leu Asp Phe Ser Val Ile Ile Met Ala Tyr Thr 195 200 205 act gaa ttt gtg gac ctg ggc aat gtc tca gcc tta cgc acc ttc cga 675 Thr Glu Phe Val Asp Leu Gly Asn Val Ser Ala Leu Arg Thr Phe Arg 210 215 220 gtc ctc cgg gcc ctg aaa act ata tca gtc att tca ggg ctg aag acc 723 Val Leu Arg Ala Leu Lys Thr Ile Ser Val Ile Ser Gly Leu Lys Thr 225 230 235 atc gtg ggg gcc ctg atc cag tct gtg aag aag ctg gct gat gtg atg 771 Ile Val Gly Ala Leu Ile Gln Ser Val Lys Lys Leu Ala Asp Val Met 240 245 250 gtc ctc aca gtc ttc tgc ctc agc gtc ttt gcc ctc atc ggc ctg cag 819 Val Leu Thr Val Phe Cys Leu Ser Val Phe Ala Leu Ile Gly Leu Gln 255 260 265 270 ctc ttc atg ggc aac cta agg cac aag tgc gtg cgc aac ttc aca gcg 867 Leu Phe Met Gly Asn Leu Arg His Lys Cys Val Arg Asn Phe Thr Ala 275 280 285 ctc aac ggc acc aac ggc tcc gtg gag gcc gac ggc ttg gtc tgg gaa 915 Leu Asn Gly Thr Asn Gly Ser Val Glu Ala Asp Gly Leu Val Trp Glu 290 295 300 tcc ctg gac ctt tac ctc agt gat cca gaa aat tac ctg ctc aag aac 963 Ser Leu Asp Leu Tyr Leu Ser Asp Pro Glu Asn Tyr Leu Leu Lys Asn 305 310 315 ggc acc tct gat gtg tta ctg tgt ggg aac agc tct gac gct ggg aca 1011 Gly Thr Ser Asp Val Leu Leu Cys Gly Asn Ser Ser Asp Ala Gly Thr 320 325 330 tgt ccg gag ggc tac cgg tgc cta aag gca ggc gag aac ccc gac cac 1059 Cys Pro Glu Gly Tyr Arg Cys Leu Lys Ala Gly Glu Asn Pro Asp His 335 340 345 350 ggc tac acc agc ttc gat tcc ttt gcc tgg gcc ttt ctt gca ctc ttc 1107 Gly Tyr Thr Ser Phe Asp Ser Phe Ala Trp Ala Phe Leu Ala Leu Phe 355 360 365 cgc ctg atg acg cag gac tgc tgg gag cgc ctc tat cag cag acc ctc 1155 Arg Leu Met Thr Gln Asp Cys Trp Glu Arg Leu Tyr Gln Gln Thr Leu 370 375 380 agg tcc gca ggg aag atc tac atg atc ttc ttc atg ctt gtc atc ttc 1203 Arg Ser Ala Gly Lys Ile Tyr Met Ile Phe Phe Met Leu Val Ile Phe 385 390 395 ctg ggg tcc ttc tac ctg gtg aac ctg atc ctg gcc gtg gtc gca atg 1251 Leu Gly Ser Phe Tyr Leu Val Asn Leu Ile Leu Ala Val Val Ala Met 400 405 410 gcc tat gag gag caa aac caa gcc acc atc gct gag acc gag gag aag 1299 Ala Tyr Glu Glu Gln Asn Gln Ala Thr Ile Ala Glu Thr Glu Glu Lys 415 420 425 430 gaa aag cgc ttc cag gag gcc atg gaa atg ctc aag aaa gaa cac gag 1347 Glu Lys Arg Phe Gln Glu Ala Met Glu Met Leu Lys Lys Glu His Glu 435 440 445 gcc ctc acc atc agg ggt gtg gat acc gtg tcc cgt agc tcc ttg gag 1395 Ala Leu Thr Ile Arg Gly Val Asp Thr Val Ser Arg Ser Ser Leu Glu 450 455 460 atg tcc cct ttg gcc cca gta aac agc cat gag aga aga agc aag agg 1443 Met Ser Pro Leu Ala Pro Val Asn Ser His Glu Arg Arg Ser Lys Arg 465 470 475 aga aaa cgg atg tct tca gga act gag gag tgt ggg gag gac agg ctc 1491 Arg Lys Arg Met Ser Ser Gly Thr Glu Glu Cys Gly Glu Asp Arg Leu 480 485 490 ccc aag tct gac tca gaa gat ggt ccc aga gca atg aat cat ctc agc 1539 Pro Lys Ser Asp Ser Glu Asp Gly Pro Arg Ala Met Asn His Leu Ser 495 500 505 510 ctc acc cgt ggc ctc agc agg act tct atg aag cca cgt tcc agc cgc 1587 Leu Thr Arg Gly Leu Ser Arg Thr Ser Met Lys Pro Arg Ser Ser Arg 515 520 525 ggg agc att ttc acc ttt cgc agg cga gac ctg ggt tct gaa gca gat 1635 Gly Ser Ile Phe Thr Phe Arg Arg Arg Asp Leu Gly Ser Glu Ala Asp 530 535 540 ttt gca gat gat gaa aac agc aca gcg ggg gag agc gag agc cac cgc 1683 Phe Ala Asp Asp Glu Asn Ser Thr Ala Gly Glu Ser Glu Ser His Arg 545 550 555 aca tca ctg ctg gtg ccc tgg ccc ctg cgc cgg acc agt gcc cag gga 1731 Thr Ser Leu Leu Val Pro Trp Pro Leu Arg Arg Thr Ser Ala Gln Gly 560 565 570 cag ccc agt ccc gga acc tcg gct cct ggc cac gcc ctc cat ggc aaa 1779 Gln Pro Ser Pro Gly Thr Ser Ala Pro Gly His Ala Leu His Gly Lys 575 580 585 590 aag aac agc act gtg gac tgc aat ggg gtg gtc tca tta ctg ggg gca 1827 Lys Asn Ser Thr Val Asp Cys Asn Gly Val Val Ser Leu Leu Gly Ala 595 600 605 ggc gac cca gag gcc aca tcc cca gga agc cac atc ctc cgc cct gtg 1875 Gly Asp Pro Glu Ala Thr Ser Pro Gly Ser His Ile Leu Arg Pro Val 610 615 620 atg cta gag cac ccg cca gac acg acc acg cca tcg gag gag cca ggc 1923 Met Leu Glu His Pro Pro Asp Thr Thr Thr Pro Ser Glu Glu Pro Gly 625 630 635 ggg ccc cag atg ctg acc tcc cag gct ccg tgt gta gat ggc ttc gag 1971 Gly Pro Gln Met Leu Thr Ser Gln Ala Pro Cys Val Asp Gly Phe Glu 640 645 650 gag cca gga gca cgg cag cgg gcc ctc agc gca gtc agc gtc ctc acc 2019 Glu Pro Gly Ala Arg Gln Arg Ala Leu Ser Ala Val Ser Val Leu Thr 655 660 665 670 agc gca ctg gaa gag tta gag gag tct cgc cac aag tgt cca cca tgc 2067 Ser Ala Leu Glu Glu Leu Glu Glu Ser Arg His Lys Cys Pro Pro Cys 675 680 685 tgg aac cgt ctc gcc cag cgc tac ctg atc tgg gag tgc tgc ccg ctg 2115 Trp Asn Arg Leu Ala Gln Arg Tyr Leu Ile Trp Glu Cys Cys Pro Leu 690 695 700 tgg atg tcc atc aag cag gga gtg aag ttg gtg gtc atg gac ccg ttt 2163 Trp Met Ser Ile Lys Gln Gly Val Lys Leu Val Val Met Asp Pro Phe 705 710 715 act gac ctc acc atc act atg tgc atc gta ctc aac aca ctc ttc atg 2211 Thr Asp Leu Thr Ile Thr Met Cys Ile Val Leu Asn Thr Leu Phe Met 720 725 730 gcg ctg gag cac tac aac atg aca agt gaa ttc gag gag atg ctg cag 2259 Ala Leu Glu His Tyr Asn Met Thr Ser Glu Phe Glu Glu Met Leu Gln 735 740 745 750 gtc gga aac ctg gtc ttc aca ggg att ttc aca gca gag atg acc ttc 2307 Val Gly Asn Leu Val Phe Thr Gly Ile Phe Thr Ala Glu Met Thr Phe 755 760 765 aag atc att gcc ctc gac ccc tac tac tac ttc caa cag ggc tgg aac 2355 Lys Ile Ile Ala Leu Asp Pro Tyr Tyr Tyr Phe Gln Gln Gly Trp Asn 770 775 780 atc ttc gac agc atc atc gtc atc ctt agc ctc atg gag ctg ggc ctg 2403 Ile Phe Asp Ser Ile Ile Val Ile Leu Ser Leu Met Glu Leu Gly Leu 785 790 795 tcc cgc atg agc aac ttg tcg gtg ctg cgc tcc ttc cgc ctg ctg cgg 2451 Ser Arg Met Ser Asn Leu Ser Val Leu Arg Ser Phe Arg Leu Leu Arg 800 805 810 gtc ttc aag ctg gcc aaa tca tgg ccc acc ctg aac aca ctc atc aag 2499 Val Phe Lys Leu Ala Lys Ser Trp Pro Thr Leu Asn Thr Leu Ile Lys 815 820 825 830 atc atc ggg aac tca gtg ggg gca ctg ggg aac ctg aca ctg gtg cta 2547 Ile Ile Gly Asn Ser Val Gly Ala Leu Gly Asn Leu Thr Leu Val Leu 835 840 845 gcc atc atc gtg ttc atc ttt gct gtg gtg ggc atg cag ctc ttt ggc 2595 Ala Ile Ile Val Phe Ile Phe Ala Val Val Gly Met Gln Leu Phe Gly 850 855 860 aag aac tac tcg gag ctg agg gac agc gac tca ggc ctg ctg cct cgc 2643 Lys Asn Tyr Ser Glu Leu Arg Asp Ser Asp Ser Gly Leu Leu Pro Arg 865 870 875 tgg cac atg atg gac ttc ttt cat gcc ttc ctc atc atc ttc cgc atc 2691 Trp His Met Met Asp Phe Phe His Ala Phe Leu Ile Ile Phe Arg Ile 880 885 890 ctc tgt gga gag tgg atc gag acc atg tgg gac tgc atg gag gtg tcg 2739 Leu Cys Gly Glu Trp Ile Glu Thr Met Trp Asp Cys Met Glu Val Ser 895 900 905 910 ggg cag tca tta tgc ctg ctg gtc ttc ttg ctt gtt atg gtc att ggc 2787 Gly Gln Ser Leu Cys Leu Leu Val Phe Leu Leu Val Met Val Ile Gly 915 920 925 aac ctt gtg gtc ctg aat ctc ttc ctg gcc ttg ctg ctc agc tcc ttc 2835 Asn Leu Val Val Leu Asn Leu Phe Leu Ala Leu Leu Leu Ser Ser Phe 930 935 940 agt gca gac aac ctc aca gcc cct gat gag gac aga gag atg aac aac 2883 Ser Ala Asp Asn Leu Thr Ala Pro Asp Glu Asp Arg Glu Met Asn Asn 945 950 955 ctc cag ctg gcc ctg gcc cgc atc cag agg ggc ctg cgc ttt gtc aag 2931 Leu Gln Leu Ala Leu Ala Arg Ile Gln Arg Gly Leu Arg Phe Val Lys 960 965 970 cgg acc acc tgg gat ttc tgc tgt ggt ctc ctg cgg cag cgg cct cag 2979 Arg Thr Thr Trp Asp Phe Cys Cys Gly Leu Leu Arg Gln Arg Pro Gln 975 980 985 990 aag ccc gca gcc ctt gcc gcc cag ggc cag ctg ccc agc tgc att gcc 3027 Lys Pro Ala Ala Leu Ala Ala Gln Gly Gln Leu Pro Ser Cys Ile Ala 995 1000 1005 acc ccc tac tcc ccg cca ccc cca gag acg gag aag gtg cct ccc acc 3075 Thr Pro Tyr Ser Pro Pro Pro Pro Glu Thr Glu Lys Val Pro Pro Thr 1010 1015 1020 cgc aag gaa aca cgg ttt gag gaa ggc gag caa cca ggc cag ggc acc 3123 Arg Lys Glu Thr Arg Phe Glu Glu Gly Glu Gln Pro Gly Gln Gly Thr 1025 1030 1035 ccc ggg gat cca gag ccc gtg tgt gtg ccc atc gct gtg gcc gag tca 3171 Pro Gly Asp Pro Glu Pro Val Cys Val Pro Ile Ala Val Ala Glu Ser 1040 1045 1050 gac aca gat gac caa gaa gaa gat gag gag aac agc ctg ggc acg gag 3219 Asp Thr Asp Asp Gln Glu Glu Asp Glu Glu Asn Ser Leu Gly Thr Glu 1055 1060 1065 1070 gag gag tcc agc aag cag gaa tcc cag cct gtg tcc ggt ggc cca gag 3267 Glu Glu Ser Ser Lys Gln Glu Ser Gln Pro Val Ser Gly Gly Pro Glu 1075 1080 1085 gcc cct ccg gat tcc agg acc tgg agc cag gtg tca gcg act gcc tcc 3315 Ala Pro Pro Asp Ser Arg Thr Trp Ser Gln Val Ser Ala Thr Ala Ser 1090 1095 1100 tct gag gcc gag gcc agt gca tct cag gcc gac tgg cgg cag cag tgg 3363 Ser Glu Ala Glu Ala Ser Ala Ser Gln Ala Asp Trp Arg Gln Gln Trp 1105 1110 1115 aaa gcg gaa ccc cag gcc cca ggg tgc ggt gag acc cca gag gac agt 3411 Lys Ala Glu Pro Gln Ala Pro Gly Cys Gly Glu Thr Pro Glu Asp Ser 1120 1125 1130 tgc tcc gag ggc agc aca gca gac atg acc aac acc gct gag ctc ctg 3459 Cys Ser Glu Gly Ser Thr Ala Asp Met Thr Asn Thr Ala Glu Leu Leu 1135 1140 1145 1150 gag cag atc cct gac ctc ggc cag gat gtc aag gac cca gag gac tgc 3507 Glu Gln Ile Pro Asp Leu Gly Gln Asp Val Lys Asp Pro Glu Asp Cys 1155 1160 1165 ttc act gaa ggc tgt gtc cgg cgc tgt ccc tgc tgt gcg gtg gac acc 3555 Phe Thr Glu Gly Cys Val Arg Arg Cys Pro Cys Cys Ala Val Asp Thr 1170 1175 1180 aca cag gcc cca ggg aag gtc tgg tgg cgg ttg cgc aag acc tgc tac 3603 Thr Gln Ala Pro Gly Lys Val Trp Trp Arg Leu Arg Lys Thr Cys Tyr 1185 1190 1195 cac atc gtg gag cac agc tgg ttc gag aca ttc atc atc ttc atg atc 3651 His Ile Val Glu His Ser Trp Phe Glu Thr Phe Ile Ile Phe Met Ile 1200 1205 1210 cta ctc agc agt gga gcg ctg gcc ttc gag gac atc tac cta gag gag 3699 Leu Leu Ser Ser Gly Ala Leu Ala Phe Glu Asp Ile Tyr Leu Glu Glu 1215 1220 1225 1230 cgg aag acc atc aag gtt ctg ctt gag tat gcc gac aag atg ttc aca 3747 Arg Lys Thr Ile Lys Val Leu Leu Glu Tyr Ala Asp Lys Met Phe Thr 1235 1240 1245 tat gtc ttc gtg ctg gag atg ctg ctc aag tgg gtg gcc tac ggc ttc 3795 Tyr Val Phe Val Leu Glu Met Leu Leu Lys Trp Val Ala Tyr Gly Phe 1250 1255 1260 aag aag tac ttc acc aat gcc tgg tgc tgg ctc gac ttc ctc atc gta 3843 Lys Lys Tyr Phe Thr Asn Ala Trp Cys Trp Leu Asp Phe Leu Ile Val 1265 1270 1275 gac gtc tct ctg gtc agc ctg gtg gcc aac acc ctg ggc ttt gcc gag 3891 Asp Val Ser Leu Val Ser Leu Val Ala Asn Thr Leu Gly Phe Ala Glu 1280 1285 1290 atg ggc ccc atc aag tca ctg cgg acg ctg cgt gca ctc cgt cct ctg 3939 Met Gly Pro Ile Lys Ser Leu Arg Thr Leu Arg Ala Leu Arg Pro Leu 1295 1300 1305 1310 aga gct ctg tca cga ttt gag ggc atg agg gtg gtg gtc aat gcc ctg 3987 Arg Ala Leu Ser Arg Phe Glu Gly Met Arg Val Val Val Asn Ala Leu 1315 1320 1325 gtg ggc gcc atc ccg tcc atc atg aac gtc ctc ctc gtc tgc ctc atc 4035 Val Gly Ala Ile Pro Ser Ile Met Asn Val Leu Leu Val Cys Leu Ile 1330 1335 1340 ttc tgg ctc atc ttc agc atc atg ggc gtg aac ctc ttt gcg ggg aag 4083 Phe Trp Leu Ile Phe Ser Ile Met Gly Val Asn Leu Phe Ala Gly Lys 1345 1350 1355 ttt ggg agg tgc atc aac cag aca gag gga gac ttg cct ttg aac tac 4131 Phe Gly Arg Cys Ile Asn Gln Thr Glu Gly Asp Leu Pro Leu Asn Tyr 1360 1365 1370 acc atc gtg aac aac aag agc cag tgt gag tcc ttg aac ttg acc gga 4179 Thr Ile Val Asn Asn Lys Ser Gln Cys Glu Ser Leu Asn Leu Thr Gly 1375 1380 1385 1390 gaa ttg tac tgg acc aag gtg aaa gtc aac ttt gac aac gtg ggg gcc 4227 Glu Leu Tyr Trp Thr Lys Val Lys Val Asn Phe Asp Asn Val Gly Ala 1395 1400 1405 ggg tac ctg gcc ctt ctg cag gtg gca aca ttt aaa ggc tgg atg gac 4275 Gly Tyr Leu Ala Leu Leu Gln Val Ala Thr Phe Lys Gly Trp Met Asp 1410 1415 1420 att atg tat gca gct gtg gac tcc agg ggg tat gaa gag cag cct cag 4323 Ile Met Tyr Ala Ala Val Asp Ser Arg Gly Tyr Glu Glu Gln Pro Gln 1425 1430 1435 tgg gaa tac aac ctc tac atg tac atc tat ttt gtc att ttc atc atc 4371 Trp Glu Tyr Asn Leu Tyr Met Tyr Ile Tyr Phe Val Ile Phe Ile Ile 1440 1445 1450 ttt ggg tct ttc ttc acc ctg aac ctc ttt att ggt gtc atc att gac 4419 Phe Gly Ser Phe Phe Thr Leu Asn Leu Phe Ile Gly Val Ile Ile Asp 1455 1460 1465 1470 aac ttc aac caa cag aag aaa aag tta ggg ggc cag gac atc ttc atg 4467 Asn Phe Asn Gln Gln Lys Lys Lys Leu Gly Gly Gln Asp Ile Phe Met 1475 1480 1485 aca gag gag cag aag aag tac tac aat gcc atg aag aag ctg ggc tcc 4515 Thr Glu Glu Gln Lys Lys Tyr Tyr Asn Ala Met Lys Lys Leu Gly Ser 1490 1495 1500 aag aag ccc cag aag ccc atc cca cgg ccc ctg aac aag tac cag ggc 4563 Lys Lys Pro Gln Lys Pro Ile Pro Arg Pro Leu Asn Lys Tyr Gln Gly 1505 1510 1515 ttc ata ttc gac att gtg acc aag cag gcc ttt gac gtc acc atc atg 4611 Phe Ile Phe Asp Ile Val Thr Lys Gln Ala Phe Asp Val Thr Ile Met 1520 1525 1530 ttt ctg atc tgc ttg aat atg gtg acc atg atg gtg gag aca gat gac 4659 Phe Leu Ile Cys Leu Asn Met Val Thr Met Met Val Glu Thr Asp Asp 1535 1540 1545 1550 caa agt cct gag aaa atc aac atc ttg gcc aag atc aac ctg ctc ttt 4707 Gln Ser Pro Glu Lys Ile Asn Ile Leu Ala Lys Ile Asn Leu Leu Phe 1555 1560 1565 gtg gcc atc ttc aca ggc gag tgt att gtc aag ctg gct gcc ctg cgc 4755 Val Ala Ile Phe Thr Gly Glu Cys Ile Val Lys Leu Ala Ala Leu Arg 1570 1575 1580 cac tac tac ttc acc aac agc tgg aat atc ttc gac ttc gtg gtt gtc 4803 His Tyr Tyr Phe Thr Asn Ser Trp Asn Ile Phe Asp Phe Val Val Val 1585 1590 1595 atc ctc tcc atc gtg ggc act gtg ctc tcg gac atc atc cag aag tac 4851 Ile Leu Ser Ile Val Gly Thr Val Leu Ser Asp Ile Ile Gln Lys Tyr 1600 1605 1610 ttc ttc tcc ccg acg ctc ttc cga gtc atc cgc ctg gcc cga ata ggc 4899 Phe Phe Ser Pro Thr Leu Phe Arg Val Ile Arg Leu Ala Arg Ile Gly 1615 1620 1625 1630 cgc atc ctc aga ctg atc cga ggg gcc aag ggg atc cgc acg ctg ctc 4947 Arg Ile Leu Arg Leu Ile Arg Gly Ala Lys Gly Ile Arg Thr Leu Leu 1635 1640 1645 ttt gcc ctc atg atg tcc ctg cct gcc ctc ttc aac atc ggg ctg ctg 4995 Phe Ala Leu Met Met Ser Leu Pro Ala Leu Phe Asn Ile Gly Leu Leu 1650 1655 1660 ctc ttc ctc gtc atg ttc atc tac tcc atc ttt ggc atg gcc aac ttc 5043 Leu Phe Leu Val Met Phe Ile Tyr Ser Ile Phe Gly Met Ala Asn Phe 1665 1670 1675 gct tat gtc aag tgg gag gct ggc atc gac gac atg ttc aac ttc cag 5091 Ala Tyr Val Lys Trp Glu Ala Gly Ile Asp Asp Met Phe Asn Phe Gln 1680 1685 1690 acc ttc gcc aac agc atg ctg tgc ctc ttc cag atc acc acg tcg gcc 5139 Thr Phe Ala Asn Ser Met Leu Cys Leu Phe Gln Ile Thr Thr Ser Ala 1695 1700 1705 1710 ggc tgg gat ggc ctc ctc agc ccc atc ctc aac act ggg ccg ccc tac 5187 Gly Trp Asp Gly Leu Leu Ser Pro Ile Leu Asn Thr Gly Pro Pro Tyr 1715 1720 1725 tgc gac ccc act ctg ccc aac agc aat ggc tct cgg ggg gac tgc ggg 5235 Cys Asp Pro Thr Leu Pro Asn Ser Asn Gly Ser Arg Gly Asp Cys Gly 1730 1735 1740 agc cca gcc gtg ggc atc ctc ttc ttc acc acc tac atc atc atc tcc 5283 Ser Pro Ala Val Gly Ile Leu Phe Phe Thr Thr Tyr Ile Ile Ile Ser 1745 1750 1755 ttc ctc atc gtg gtc aac atg tac att gcc atc atc ctg gag aac ttc 5331 Phe Leu Ile Val Val Asn Met Tyr Ile Ala Ile Ile Leu Glu Asn Phe 1760 1765 1770 agc gtg gcc acg gag gag agc acc gag ccc ctg agt gag gac gac ttc 5379 Ser Val Ala Thr Glu Glu Ser Thr Glu Pro Leu Ser Glu Asp Asp Phe 1775 1780 1785 1790 gat atg ttc tat gag atc tgg gag aaa ttt gac cca gag gcc act cag 5427 Asp Met Phe Tyr Glu Ile Trp Glu Lys Phe Asp Pro Glu Ala Thr Gln 1795 1800 1805 ttt att gag tat tcg gtc ctg tct gac ttt gcc gat gcc ctg tct gag 5475 Phe Ile Glu Tyr Ser Val Leu Ser Asp Phe Ala Asp Ala Leu Ser Glu 1810 1815 1820 cca ctc cgt atc gcc aag ccc aac cag ata agc ctc atc aac atg gac 5523 Pro Leu Arg Ile Ala Lys Pro Asn Gln Ile Ser Leu Ile Asn Met Asp 1825 1830 1835 ctg ccc atg gtg agt ggg gac cgc atc cat tgc atg gac att ctc ttt 5571 Leu Pro Met Val Ser Gly Asp Arg Ile His Cys Met Asp Ile Leu Phe 1840 1845 1850 gcc ttc acc aaa agg gtc ctg ggg gag tct ggg gag atg gac gcc ctg 5619 Ala Phe Thr Lys Arg Val Leu Gly Glu Ser Gly Glu Met Asp Ala Leu 1855 1860 1865 1870 aag atc cag atg gag gag aag ttc atg gca gcc aac cca tcc aag atc 5667 Lys Ile Gln Met Glu Glu Lys Phe Met Ala Ala Asn Pro Ser Lys Ile 1875 1880 1885 tcc tac gag ccc atc acc acc aca ctc cgg cgc aag cac gaa gag gtg 5715 Ser Tyr Glu Pro Ile Thr Thr Thr Leu Arg Arg Lys His Glu Glu Val 1890 1895 1900 tcg gcc atg gtt atc cag aga gcc ttc cgc agg cac ctg ctg caa cgc 5763 Ser Ala Met Val Ile Gln Arg Ala Phe Arg Arg His Leu Leu Gln Arg 1905 1910 1915 tct ttg aag cat gcc tcc ttc ctc ttc cgt cag cag gcg ggc agc ggc 5811 Ser Leu Lys His Ala Ser Phe Leu Phe Arg Gln Gln Ala Gly Ser Gly 1920 1925 1930 ctc tcc gaa gag gat gcc cct gag cga gag ggc ctc atc gcc tac gtg 5859 Leu Ser Glu Glu Asp Ala Pro Glu Arg Glu Gly Leu Ile Ala Tyr Val 1935 1940 1945 1950 atg agt gag aac ttc tcc cga ccc ctt ggc cca ccc tcc agc tcc tcc 5907 Met Ser Glu Asn Phe Ser Arg Pro Leu Gly Pro Pro Ser Ser Ser Ser 1955 1960 1965 atc tcc tcc act tcc ttc cca ccc tcc tat gac agt gtc act aga gcc 5955 Ile Ser Ser Thr Ser Phe Pro Pro Ser Tyr Asp Ser Val Thr Arg Ala 1970 1975 1980 acc agc gat aac ctc cag gtg cgg ggg tct gac tac agc cac agt gaa 6003 Thr Ser Asp Asn Leu Gln Val Arg Gly Ser Asp Tyr Ser His Ser Glu 1985 1990 1995 gat ctc gcc gac ttc ccc cct tct ccg gac agg gac cgt gag tcc atc 6051 Asp Leu Ala Asp Phe Pro Pro Ser Pro Asp Arg Asp Arg Glu Ser Ile 2000 2005 2010 gtg tgagcctcgg cctggctggc caggacacac tgaaaag 6091 Val 2015 2 2015 PRT Homo sapiens 2 Met Ala Asn Phe Leu Leu Pro Arg Gly Thr Ser Ser Phe Arg Arg Phe 1 5 10 15 Thr Arg Glu Ser Leu Ala Ala Ile Glu Lys Arg Met Ala Glu Lys Gln 20 25 30 Ala Arg Gly Ser Thr Thr Leu Gln Glu Ser Arg Glu Gly Leu Pro Glu 35 40 45 Glu Glu Ala Pro Arg Pro Gln Leu Asp Leu Gln Ala Ser Lys Lys Leu 50 55 60 Pro Asp Leu Tyr Gly Asn Pro Pro Gln Glu Leu Ile Gly Glu Pro Leu 65 70 75 80 Glu Asp Leu Asp Pro Phe Tyr Ser Thr Gln Lys Thr Phe Ile Val Leu 85 90 95 Asn Lys Gly Lys Thr Ile Phe Arg Phe Ser Ala Thr Asn Ala Leu Tyr 100 105 110 Val Leu Ser Pro Phe His Pro Ile Arg Arg Ala Ala Val Lys Ile Leu 115 120 125 Val His Ser Leu Phe Asn Met Leu Ile Met Cys Thr Ile Leu Thr Asn 130 135 140 Cys Val Phe Met Ala Gln His Asp Pro Pro Pro Trp Thr Lys Tyr Val 145 150 155 160 Glu Tyr Thr Phe Thr Ala Ile Tyr Thr Phe Glu Ser Leu Val Lys Ile 165 170 175 Leu Ala Arg Gly Phe Cys Leu His Ala Phe Thr Phe Leu Arg Asp Pro 180 185 190 Trp Asn Trp Leu Asp Phe Ser Val Ile Ile Met Ala Tyr Thr Thr Glu 195 200 205 Phe Val Asp Leu Gly Asn Val Ser Ala Leu Arg Thr Phe Arg Val Leu 210 215 220 Arg Ala Leu Lys Thr Ile Ser Val Ile Ser Gly Leu Lys Thr Ile Val 225 230 235 240 Gly Ala Leu Ile Gln Ser Val Lys Lys Leu Ala Asp Val Met Val Leu 245 250 255 Thr Val Phe Cys Leu Ser Val Phe Ala Leu Ile Gly Leu Gln Leu Phe 260 265 270 Met Gly Asn Leu Arg His Lys Cys Val Arg Asn Phe Thr Ala Leu Asn 275 280 285 Gly Thr Asn Gly Ser Val Glu Ala Asp Gly Leu Val Trp Glu Ser Leu 290 295 300 Asp Leu Tyr Leu Ser Asp Pro Glu Asn Tyr Leu Leu Lys Asn Gly Thr 305 310 315 320 Ser Asp Val Leu Leu Cys Gly Asn Ser Ser Asp Ala Gly Thr Cys Pro 325 330 335 Glu Gly Tyr Arg Cys Leu Lys Ala Gly Glu Asn Pro Asp His Gly Tyr 340 345 350 Thr Ser Phe Asp Ser Phe Ala Trp Ala Phe Leu Ala Leu Phe Arg Leu 355 360 365 Met Thr Gln Asp Cys Trp Glu Arg Leu Tyr Gln Gln Thr Leu Arg Ser 370 375 380 Ala Gly Lys Ile Tyr Met Ile Phe Phe Met Leu Val Ile Phe Leu Gly 385 390 395 400 Ser Phe Tyr Leu Val Asn Leu Ile Leu Ala Val Val Ala Met Ala Tyr 405 410 415 Glu Glu Gln Asn Gln Ala Thr Ile Ala Glu Thr Glu Glu Lys Glu Lys 420 425 430 Arg Phe Gln Glu Ala Met Glu Met Leu Lys Lys Glu His Glu Ala Leu 435 440 445 Thr Ile Arg Gly Val Asp Thr Val Ser Arg Ser Ser Leu Glu Met Ser 450 455 460 Pro Leu Ala Pro Val Asn Ser His Glu Arg Arg Ser Lys Arg Arg Lys 465 470 475 480 Arg Met Ser Ser Gly Thr Glu Glu Cys Gly Glu Asp Arg Leu Pro Lys 485 490 495 Ser Asp Ser Glu Asp Gly Pro Arg Ala Met Asn His Leu Ser Leu Thr 500 505 510 Arg Gly Leu Ser Arg Thr Ser Met Lys Pro Arg Ser Ser Arg Gly Ser 515 520 525 Ile Phe Thr Phe Arg Arg Arg Asp Leu Gly Ser Glu Ala Asp Phe Ala 530 535 540 Asp Asp Glu Asn Ser Thr Ala Gly Glu Ser Glu Ser His Arg Thr Ser 545 550 555 560 Leu Leu Val Pro Trp Pro Leu Arg Arg Thr Ser Ala Gln Gly Gln Pro 565 570 575 Ser Pro Gly Thr Ser Ala Pro Gly His Ala Leu His Gly Lys Lys Asn 580 585 590 Ser Thr Val Asp Cys Asn Gly Val Val Ser Leu Leu Gly Ala Gly Asp 595 600 605 Pro Glu Ala Thr Ser Pro Gly Ser His Ile Leu Arg Pro Val Met Leu 610 615 620 Glu His Pro Pro Asp Thr Thr Thr Pro Ser Glu Glu Pro Gly Gly Pro 625 630 635 640 Gln Met Leu Thr Ser Gln Ala Pro Cys Val Asp Gly Phe Glu Glu Pro 645 650 655 Gly Ala Arg Gln Arg Ala Leu Ser Ala Val Ser Val Leu Thr Ser Ala 660 665 670 Leu Glu Glu Leu Glu Glu Ser Arg His Lys Cys Pro Pro Cys Trp Asn 675 680 685 Arg Leu Ala Gln Arg Tyr Leu Ile Trp Glu Cys Cys Pro Leu Trp Met 690 695 700 Ser Ile Lys Gln Gly Val Lys Leu Val Val Met Asp Pro Phe Thr Asp 705 710 715 720 Leu Thr Ile Thr Met Cys Ile Val Leu Asn Thr Leu Phe Met Ala Leu 725 730 735 Glu His Tyr Asn Met Thr Ser Glu Phe Glu Glu Met Leu Gln Val Gly 740 745 750 Asn Leu Val Phe Thr Gly Ile Phe Thr Ala Glu Met Thr Phe Lys Ile 755 760 765 Ile Ala Leu Asp Pro Tyr Tyr Tyr Phe Gln Gln Gly Trp Asn Ile Phe 770 775 780 Asp Ser Ile Ile Val Ile Leu Ser Leu Met Glu Leu Gly Leu Ser Arg 785 790 795 800 Met Ser Asn Leu Ser Val Leu Arg Ser Phe Arg Leu Leu Arg Val Phe 805 810 815 Lys Leu Ala Lys Ser Trp Pro Thr Leu Asn Thr Leu Ile Lys Ile Ile 820 825 830 Gly Asn Ser Val Gly Ala Leu Gly Asn Leu Thr Leu Val Leu Ala Ile 835 840 845 Ile Val Phe Ile Phe Ala Val Val Gly Met Gln Leu Phe Gly Lys Asn 850 855 860 Tyr Ser Glu Leu Arg Asp Ser Asp Ser Gly Leu Leu Pro Arg Trp His 865 870 875 880 Met Met Asp Phe Phe His Ala Phe Leu Ile Ile Phe Arg Ile Leu Cys 885 890 895 Gly Glu Trp Ile Glu Thr Met Trp Asp Cys Met Glu Val Ser Gly Gln 900 905 910 Ser Leu Cys Leu Leu Val Phe Leu Leu Val Met Val Ile Gly Asn Leu 915 920 925 Val Val Leu Asn Leu Phe Leu Ala Leu Leu Leu Ser Ser Phe Ser Ala 930 935 940 Asp Asn Leu Thr Ala Pro Asp Glu Asp Arg Glu Met Asn Asn Leu Gln 945 950 955 960 Leu Ala Leu Ala Arg Ile Gln Arg Gly Leu Arg Phe Val Lys Arg Thr 965 970 975 Thr Trp Asp Phe Cys Cys Gly Leu Leu Arg Gln Arg Pro Gln Lys Pro 980 985 990 Ala Ala Leu Ala Ala Gln Gly Gln Leu Pro Ser Cys Ile Ala Thr Pro 995 1000 1005 Tyr Ser Pro Pro Pro Pro Glu Thr Glu Lys Val Pro Pro Thr Arg Lys 1010 1015 1020 Glu Thr Arg Phe Glu Glu Gly Glu Gln Pro Gly Gln Gly Thr Pro Gly 1025 1030 1035 1040 Asp Pro Glu Pro Val Cys Val Pro Ile Ala Val Ala Glu Ser Asp Thr 1045 1050 1055 Asp Asp Gln Glu Glu Asp Glu Glu Asn Ser Leu Gly Thr Glu Glu Glu 1060 1065 1070 Ser Ser Lys Gln Glu Ser Gln Pro Val Ser Gly Gly Pro Glu Ala Pro 1075 1080 1085 Pro Asp Ser Arg Thr Trp Ser Gln Val Ser Ala Thr Ala Ser Ser Glu 1090 1095 1100 Ala Glu Ala Ser Ala Ser Gln Ala Asp Trp Arg Gln Gln Trp Lys Ala 1105 1110 1115 1120 Glu Pro Gln Ala Pro Gly Cys Gly Glu Thr Pro Glu Asp Ser Cys Ser 1125 1130 1135 Glu Gly Ser Thr Ala Asp Met Thr Asn Thr Ala Glu Leu Leu Glu Gln 1140 1145 1150 Ile Pro Asp Leu Gly Gln Asp Val Lys Asp Pro Glu Asp Cys Phe Thr 1155 1160 1165 Glu Gly Cys Val Arg Arg Cys Pro Cys Cys Ala Val Asp Thr Thr Gln 1170 1175 1180 Ala Pro Gly Lys Val Trp Trp Arg Leu Arg Lys Thr Cys Tyr His Ile 1185 1190 1195 1200 Val Glu His Ser Trp Phe Glu Thr Phe Ile Ile Phe Met Ile Leu Leu 1205 1210 1215 Ser Ser Gly Ala Leu Ala Phe Glu Asp Ile Tyr Leu Glu Glu Arg Lys 1220 1225 1230 Thr Ile Lys Val Leu Leu Glu Tyr Ala Asp Lys Met Phe Thr Tyr Val 1235 1240 1245 Phe Val Leu Glu Met Leu Leu Lys Trp Val Ala Tyr Gly Phe Lys Lys 1250 1255 1260 Tyr Phe Thr Asn Ala Trp Cys Trp Leu Asp Phe Leu Ile Val Asp Val 1265 1270 1275 1280 Ser Leu Val Ser Leu Val Ala Asn Thr Leu Gly Phe Ala Glu Met Gly 1285 1290 1295 Pro Ile Lys Ser Leu Arg Thr Leu Arg Ala Leu Arg Pro Leu Arg Ala 1300 1305 1310 Leu Ser Arg Phe Glu Gly Met Arg Val Val Val Asn Ala Leu Val Gly 1315 1320 1325 Ala Ile Pro Ser Ile Met Asn Val Leu Leu Val Cys Leu Ile Phe Trp 1330 1335 1340 Leu Ile Phe Ser Ile Met Gly Val Asn Leu Phe Ala Gly Lys Phe Gly 1345 1350 1355 1360 Arg Cys Ile Asn Gln Thr Glu Gly Asp Leu Pro Leu Asn Tyr Thr Ile 1365 1370 1375 Val Asn Asn Lys Ser Gln Cys Glu Ser Leu Asn Leu Thr Gly Glu Leu 1380 1385 1390 Tyr Trp Thr Lys Val Lys Val Asn Phe Asp Asn Val Gly Ala Gly Tyr 1395 1400 1405 Leu Ala Leu Leu Gln Val Ala Thr Phe Lys Gly Trp Met Asp Ile Met 1410 1415 1420 Tyr Ala Ala Val Asp Ser Arg Gly Tyr Glu Glu Gln Pro Gln Trp Glu 1425 1430 1435 1440 Tyr Asn Leu Tyr Met Tyr Ile Tyr Phe Val Ile Phe Ile Ile Phe Gly 1445 1450 1455 Ser Phe Phe Thr Leu Asn Leu Phe Ile Gly Val Ile Ile Asp Asn Phe 1460 1465 1470 Asn Gln Gln Lys Lys Lys Leu Gly Gly Gln Asp Ile Phe Met Thr Glu 1475 1480 1485 Glu Gln Lys Lys Tyr Tyr Asn Ala Met Lys Lys Leu Gly Ser Lys Lys 1490 1495 1500 Pro Gln Lys Pro Ile Pro Arg Pro Leu Asn Lys Tyr Gln Gly Phe Ile 1505 1510 1515 1520 Phe Asp Ile Val Thr Lys Gln Ala Phe Asp Val Thr Ile Met Phe Leu 1525 1530 1535 Ile Cys Leu Asn Met Val Thr Met Met Val Glu Thr Asp Asp Gln Ser 1540 1545 1550 Pro Glu Lys Ile Asn Ile Leu Ala Lys Ile Asn Leu Leu Phe Val Ala 1555 1560 1565 Ile Phe Thr Gly Glu Cys Ile Val Lys Leu Ala Ala Leu Arg His Tyr 1570 1575 1580 Tyr Phe Thr Asn Ser Trp Asn Ile Phe Asp Phe Val Val Val Ile Leu 1585 1590 1595 1600 Ser Ile Val Gly Thr Val Leu Ser Asp Ile Ile Gln Lys Tyr Phe Phe 1605 1610 1615 Ser Pro Thr Leu Phe Arg Val Ile Arg Leu Ala Arg Ile Gly Arg Ile 1620 1625 1630 Leu Arg Leu Ile Arg Gly Ala Lys Gly Ile Arg Thr Leu Leu Phe Ala 1635 1640 1645 Leu Met Met Ser Leu Pro Ala Leu Phe Asn Ile Gly Leu Leu Leu Phe 1650 1655 1660 Leu Val Met Phe Ile Tyr Ser Ile Phe Gly Met Ala Asn Phe Ala Tyr 1665 1670 1675 1680 Val Lys Trp Glu Ala Gly Ile Asp Asp Met Phe Asn Phe Gln Thr Phe 1685 1690 1695 Ala Asn Ser Met Leu Cys Leu Phe Gln Ile Thr Thr Ser Ala Gly Trp 1700 1705 1710 Asp Gly Leu Leu Ser Pro Ile Leu Asn Thr Gly Pro Pro Tyr Cys Asp 1715 1720 1725 Pro Thr Leu Pro Asn Ser Asn Gly Ser Arg Gly Asp Cys Gly Ser Pro 1730 1735 1740 Ala Val Gly Ile Leu Phe Phe Thr Thr Tyr Ile Ile Ile Ser Phe Leu 1745 1750 1755 1760 Ile Val Val Asn Met Tyr Ile Ala Ile Ile Leu Glu Asn Phe Ser Val 1765 1770 1775 Ala Thr Glu Glu Ser Thr Glu Pro Leu Ser Glu Asp Asp Phe Asp Met 1780 1785 1790 Phe Tyr Glu Ile Trp Glu Lys Phe Asp Pro Glu Ala Thr Gln Phe Ile 1795 1800 1805 Glu Tyr Ser Val Leu Ser Asp Phe Ala Asp Ala Leu Ser Glu Pro Leu 1810 1815 1820 Arg Ile Ala Lys Pro Asn Gln Ile Ser Leu Ile Asn Met Asp Leu Pro 1825 1830 1835 1840 Met Val Ser Gly Asp Arg Ile His Cys Met Asp Ile Leu Phe Ala Phe 1845 1850 1855 Thr Lys Arg Val Leu Gly Glu Ser Gly Glu Met Asp Ala Leu Lys Ile 1860 1865 1870 Gln Met Glu Glu Lys Phe Met Ala Ala Asn Pro Ser Lys Ile Ser Tyr 1875 1880 1885 Glu Pro Ile Thr Thr Thr Leu Arg Arg Lys His Glu Glu Val Ser Ala 1890 1895 1900 Met Val Ile Gln Arg Ala Phe Arg Arg His Leu Leu Gln Arg Ser Leu 1905 1910 1915 1920 Lys His Ala Ser Phe Leu Phe Arg Gln Gln Ala Gly Ser Gly Leu Ser 1925 1930 1935 Glu Glu Asp Ala Pro Glu Arg Glu Gly Leu Ile Ala Tyr Val Met Ser 1940 1945 1950 Glu Asn Phe Ser Arg Pro Leu Gly Pro Pro Ser Ser Ser Ser Ile Ser 1955 1960 1965 Ser Thr Ser Phe Pro Pro Ser Tyr Asp Ser Val Thr Arg Ala Thr Ser 1970 1975 1980 Asp Asn Leu Gln Val Arg Gly Ser Asp Tyr Ser His Ser Glu Asp Leu 1985 1990 1995 2000 Ala Asp Phe Pro Pro Ser Pro Asp Arg Asp Arg Glu Ser Ile Val 2005 2010 2015 3 22 DNA Artificial Sequence Description of Artificial Sequence primer 3 gatgagaaga tggcaaactt cc 22 4 22 DNA Artificial Sequence Description of Artificial Sequence primer 4 gctctggatc cccgggggtg cc 22 5 20 DNA Artificial Sequence Description of Artificial Sequence primer 5 cacccccggg gatccagagc 20 6 19 DNA Artificial Sequence Description of Artificial Sequence primer 6 ttcagtgtgt cctggccag 19 7 33 DNA Artificial Sequence Description of Artificial Sequence primer 7 ttcctcatcg tggttaacct gtacattgcc atc 33 8 20 DNA Artificial Sequence Description of Artificial Sequence primer 8 ggagatgatg atgtaggtgg 20 9 25 DNA Artificial Sequence Description of Artificial Sequence primer 9 cgagagccac cgcgcatcac tgctg 25 10 23 DNA Artificial Sequence Description of Artificial Sequence primer 10 ctctcccccg ctgtgctgtt ttc 23 

We claim:
 1. An isolated polypeptide comprising a sequence selected from the group consisting of SEQ ID NO: 2 and SEQ ID NO: 2 carrying a conservative substitution, deletion or rearrangement at one or more non-critical amino acid position.
 2. An isolated polynucleotide that encodes a polypeptide comprising a sequence selected from the group consisting of SEQ ID NO: 2 and SEQ ID NO: 2 carrying a conservative substitution, deletion or rearrangement at one or more non-critical amino acid position.
 3. The isolated polynucleotide of claim 2 comprising SEQ ID NO:
 1. 4. The isolated polynucleotide of claim 2 operably linked to a non-native expression control sequence.
 5. A cultured cell comprising a polynucleotide that encodes a polypeptide of claim
 1. 6. The cultured cell of claim 5 comprising a polynucleotide that encodes a polypeptide that comprises a sequence selected from the group consisting of SEQ ID NO: 2 and SEQ ID NO: 2 carrying a conservative substitution, deletion or rearrangement at one or more non-critical amino acid position, the polynucleotide being operably linked to a non-native expression control.
 7. An isolated nucleic acid comprising at least 20 contiguous nucleotides of SEQ ID NO: 1 including at least one of a codon that encodes amino acid 558 and a codon that encodes amino acid
 618. 8. An antibody that binds specifically to an immunogenic fragment of SEQ ID NO: 2 that contains at least one of amino acid 558 and amino acid 618 of SEQ ID NO: 2
 9. A method for producing a polypeptide comprising a sequence selected from the group consisting of SEQ ID NO: 2 and SEQ ID NO: 2 carrying a conservative substitution, deletion or rearrangement at one or more non-critical amino acid position, the method comprising the step of culturing the cell of claim 6 under conditions permitting expression of the polypeptide.
 10. A method for identifying an agent that can alter the activity of a sodium channel relative to a standard, the method comprising the steps of: providing a cultured cell comprising a polynucleotide that encodes a polypeptide comprising a sequence selected from the group consisting of SEQ ID NO: 2 and SEQ ID NO: 2 carrying a conservative substitution, deletion or rearrangement at one or more non-critical amino acid position, the polynucleotide being operably linked to a non-native expression control sequence; producing the polypeptide in the cell; exposing the cell to the agent; and determining the sodium channel activity of the cell, an alteration in sodium channel activity being an indication that the agent is an activity-altering agent.
 11. The method of claim 10, wherein the determining step comprises the step of measuring a parameter selected from the group consisting of a sodium current across a cellular membrane, a membrane potential, and an intracellular sodium level.
 12. The method of claim 10, wherein the alteration is a decrease in sodium channel activity.
 13. The method of claim 10, wherein the alteration is a increase in sodium channel activity.
 14. A method for determining whether a biological sample contains an hH1b form of a sodium channel α subunit, the method comprising the steps of: contacting the sample with an hH1b-specific antibody; and determining whether the antibody specifically binds to a component in the sample, said binding being an indication that the sample contains the hH1b form of the sodium channel a subunit.
 15. A method for determining whether a human or non-human subject is at risk for Long QT syndrome, the method comprising the step of: determining whether the subject carries an hH1b form of an SCN5A gene. 